So many docker containers I use at work just have a ton of apt-get or yum statements (depending on a debian or centos base) and people rarely pin dependency versions. I really feel for the "repeatable build" issue, not to mention dependency rot.

If you want to keep things up to date, there are many examples scripts out there that either 1) checking to see if your base container is out of date (if someone updated jessie:8, you should rebuild) and 2) checking if any packages are out of date (sometimes limiting to just security updates) meaning you run apk, yum, apt, etc. within each container (or extract their package lists and examine them outside the container).

You gain a lot in the isolation, but debugging can become more difficult and you've introduced new areas of dependency rot.

I generally like containers, but hate how there are so many different orchestration formats (k8s, marathon, nomad, swarm, etc.) many different network layers (weave, flannel, etc.) and many different ways to package/fit components together (CoreOS, DC/OS, etc.)

The ecosystem is messy.